Puddle
Member
I'm trying to communicate with a heating controller over Modbus RTU (RS485) but I'm running into the common issue of having no Rx light.
S7-1200 CPU, CM1241. Heating controller is an Ascon K85, coms manual here:
https://arxivar.ascontecnologic.com/Default.aspx?doctype=MAN.INSTALLA&Testo179_1=P_K-Series_E_--
I'm just using the MB_COMM_LOAD and MB_MASTER blocks, with the master in a cyclic interupt OB because the TIA helper said it should be.
Wiring connection is Pin 8 to terminal A, Pin 3 to terminal B and Pin 1 to GND. 120ohm resistor in place between A and B.
In the coms manual for the heating controller it says to use function code 3 to get to what I need, which is the first holding registers on page 13, so I've used mode 0 and started my address at 40001.
I've tried reversing the cable connections and got two flashing amber lights.
I've tried several different addresses such as 1, 10001, 40513 etc.
Tx is flashing, Rx is not. I can see my comm load is done but my master block is busy, so I'm either sending it to the wrong address or I've connected it wrong?
S7-1200 CPU, CM1241. Heating controller is an Ascon K85, coms manual here:
https://arxivar.ascontecnologic.com/Default.aspx?doctype=MAN.INSTALLA&Testo179_1=P_K-Series_E_--
I'm just using the MB_COMM_LOAD and MB_MASTER blocks, with the master in a cyclic interupt OB because the TIA helper said it should be.
Wiring connection is Pin 8 to terminal A, Pin 3 to terminal B and Pin 1 to GND. 120ohm resistor in place between A and B.
In the coms manual for the heating controller it says to use function code 3 to get to what I need, which is the first holding registers on page 13, so I've used mode 0 and started my address at 40001.
I've tried reversing the cable connections and got two flashing amber lights.
I've tried several different addresses such as 1, 10001, 40513 etc.
Tx is flashing, Rx is not. I can see my comm load is done but my master block is busy, so I'm either sending it to the wrong address or I've connected it wrong?